WASHINGTON, Sept 28: Astronomers who stumbled upon a powerful burst of radio waves said on Thursday they had never seen anything like it before, and it could offer a new way to search for colliding stars or dying black holes.

They were searching for pulsars -- a type of rotating compacted neutron star that sends out rhythmic pulses of radiation -- when they spotted the giant radio signal.

It was extremely brief but very strong, and appears to have come from about 3 billion light-years away -- a light-year being the distance light travels in a year, or about 10 trillion kilometres.

“This burst appears to have originated from the distant universe and may have been produced by an exotic event such as the collision of two neutron stars or the death throes of an evaporating black hole,” said Duncan Lorimer of West Virginia University and the National Radio Astronomy Observatory.

Writing in the journal Science, Lorimer and colleagues said they were looking at old scans done by the Parkes radio telescope in Australia when they spotted the burst.

The burst appears to have lasted five milliseconds and may be the radio fingerprint of a single event such as a supernova or the collision of black holes, the astronomers said.

“This burst represents an entirely new astronomical phenomenon,” Matthew Bailes of Swinburne University in Australia said in a statement.

Maura McLaughlin of West Virginia University said the event is probably not rare.

“We think there are probably many of these bursts every day that we are just not detecting because we don’t have the right kind of surveys of the sky looking for them,” McLaughlin said in a telephone interview.

While satellites are detecting x-ray and gamma-ray bursts with regular surveys of large portions of the sky, radio telescopes generally focus on a very narrow field, she said.

“We are really not sure (what it is),” McLaughlin said.

“We think it has got to be some sort of catastrophic event happening in another galaxy — like two stars colliding and merging or maybe a black hole. Something kind of exotic,” she said.—Reuters